This invention relates to a document information filing system capable of optically reading image information such as from original documents, storing the document information, and optionally retrieving and displaying or printing out the stored document information.
Recently there have been developed document information filing systems in which a plurality of image information including documents are read by two-dimensional optical scanning apparatus, stored in a large-capacity image information memory device such as a video tape recorder, and optionally retrieved for display and or printing in hard copy.
In such document information filing system, an endless magnetic cassette tape having multiple tracks is set in the video tape recorder for use as the image information memory device, the magnetic cassette tape is driven at a high speed, and a magnetic head is moved in a direction at right angles to the running direction of the tape to select a desired magnetic track of the tape. Image information are recorded on the selected magnetic track for each page of original documents being stored, or previously recorded image information are read out from the magnetic track. At least one of a number of magnetic tracks of the magnetic tape is used as an index magnetic track on which a specific index information corresponding to an image information is recorded when such image information is recorded on a magnetic track for image information recording. The index information is used for referring to a desired image information among a great number of recording image information. In such reference, according to a known information filing system, an index information is first retrieved, and then the desired image information is searched for in accordance with the detected index information. According to such a known method, however, the index information cannot sometimes be decoded since the tape runs at a high speed. Namely, the running speed of the tape is higher than the index information decoding speed, so that the tape may proceed to the next index information while an index information is being decoded, thereby prohibiting the preceding index information from being decoded.
With the prior art document information filing system, moreover, the magnetic tape is searched for an index information with recording of every image information, so that it takes a lot of time to read out a number of image information.